Information handling system housing heat spreader

ABSTRACT

Thermal energy exposed at the outer surface of an information handling system housing is managed by spreading the thermal energy across the housing X and Y axes while restricting heat transfer from the housing at the Z axis. For example, a graphene outer surface couples to an aerogel substrate strengthened by a carbon fiber laminate. The graphene spreads thermal energy that escapes through the housing across the housing outer surface to limit the impact of thermal energy at any particular location, such as proximate to the location of a processor.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates in general to the field of informationhandling system housings, and more particularly to an informationhandling system housing heat spreader.

Description of the Related Art

As the value and use of information continues to increase, individualsand businesses seek additional ways to process and store information.One option available to users is information handling systems. Aninformation handling system generally processes, compiles, stores,and/or communicates information or data for business, personal, or otherpurposes thereby allowing users to take advantage of the value of theinformation. Because technology and information handling needs andrequirements vary between different users or applications, informationhandling systems may also vary regarding what information is handled,how the information is handled, how much information is processed,stored, or communicated, and how quickly and efficiently the informationmay be processed, stored, or communicated. The variations in informationhandling systems allow for information handling systems to be general orconfigured for a specific user or specific use such as financialtransaction processing, airline reservations, enterprise data storage,or global communications. In addition, information handling systems mayinclude a variety of hardware and software components that may beconfigured to process, store, and communicate information and mayinclude one or more computer systems, data storage systems, andnetworking systems.

Portable information handling systems are built in housings designed tohave minimal footprint. Tablet information handling systems are one typeof portable information handling system in which a planar housingintegrates a touch screen that acts as the primary input/output (I/O)device. Relatively small tablets provide convenient reading devices andhandle simple tasks on-the-go, such as web browsing and e-mail.Smartphones are an example of a small tablet that also provides mobiletelephone communications. Portable information handling systems thathandle more intensive computing operations, such as word processing,graphics design, spread sheet analysis, etc . . . , typically have ahousing with an integrated keyboard and a greater size that allows roomto contain more powerful processing components. Generally, as processingcapability increases housing size for containing processing componentsalso tends to increase. Users generally weigh convenience associatedwith smaller housings against processing capabilities associated withlarger housings when selecting an information handling system.

One constraint on the use of powerful components in a housing is theamount of heat that the components generate as a byproduct of electricalpower consumption. Central processing units (CPUs) provide an example ofthis since greater processing speeds tend to consume greater power and,as a result, release greater amounts of heat as a byproduct. Heatgenerated by a CPU can cause failure of an information handling systemdue to excessive internal temperatures unless the heat escapes thehousing. In addition, heat concentrated around the location of a CPU orother heat-generating component can cause discomfort to end users whotouch the housing near the position of the CPU.

One reason for the use of a larger housing with more powerful componentsis that a larger housing generally allows the use of active heatdissipation to remove heat from within the housing. A common active heatdissipation system is an internal cooling fan that blows a coolingairflow over heated components to help remove thermal energy. Passiveheat dissipation, such as heat pipes and heat sinks, generally does nottransfer thermal energy out of a housing as effectively as active heatdissipation. Thus, information handling system designers often facedifficult constraints when attempting to build portable informationhandling systems that provide adequate management of excess thermalenergy. Thin form factor information handling systems that lack adequateroom for active heat dissipation systems, such as cooling fans, tend tohave CPUs and other processing components with less robust processingcapabilities so that internal and external housing temperatures will notexceed safe limits.

SUMMARY OF THE INVENTION

Therefore a need has arisen for a system and method which supportsspreading of thermal energy across an information handling systemhousing external surface to limit concentrations of thermal energy, suchas heat spots proximate the location of a CPU disposed in the housing.

In accordance with the present invention, a system and method areprovided which substantially reduce the disadvantages and problemsassociated with previous methods and systems for dissipating heat in apassive manner at an information handling system's or other electronicdevice's housing. A heat-spreading outer surface spreads thermal energyacross the outer surface of the information handling system whilelimiting transfer of thermal energy outwards from the housing. Theheat-spreading outer surface reduces concentrations of thermal energy inhot spots that might cause discomfort to an end user and reduces thermaltransfer out from the housing for reduce impact on an end user whenhigher temperatures do exist.

More specifically, an electronic device housing supports electroniccomponents that generate heat as a byproduct of electric powerconsumption. For example, an information handling system housing havinga tablet form factor supports processing components that cooperate toprocess information, such as CPU and memory. Excess thermal energygenerated by the processing components has a restricted impact on enduser interactions with the housing. As this excess thermal energy istransported to the surface of the housing via thermal conduction, tomanage and minimize the hot spot an innovative approach to manage theenergy transfer has been created to minimize the through planeconductivity and maximize the surface cooling area. For example, asilicon or carbon based aerogel is laminated with a supporting material,such as carbon fiber, to insulate thermal energy generated within thehousing from escaping to the housing outer surface. A graphene outersurface layer is laminated to the supporting material or the insulatingmaterial so that thermal energy escaping to the housing outer surface isspread across the outer surface to avoid the presence of hot spots, suchas concentrations of thermal energy proximate the location of aprocessor or other relatively high thermal energy source. The grapheneouter surface layer couples to substrate housing material with anadhesive or as an integrated layer using a lamination, such aspolyurethane and a heated press.

The present invention provides a number of important technicaladvantages. One example of an important technical advantage is that alight weight carbon fiber housing suitable for use in thin form factorinformation handling systems passively dissipates heat along an outersurface of the housing to prevent thermal hot spots, such as may occurnear the location of a CPU. A graphene layer located at the outersurface conducts thermal energy in X and Y axes parallel to the outersurface while having limited thermal energy conduction out a Z axisperpendicular to the outer surface. Limited thermal energy conductionout the Z axis reduces the impact of heat spots located along the outersurface, such as proximate the location of a CPU. Rapid and efficientthermal dissipation along the X and Y axes reduces the concentration ofthermal energy at any particular location, instead spreading the thermalenergy along the surface to provide lower peak temperatures at locationshaving concentrated thermal energy, such as proximate a CPU disposed inthe interior of the housing.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may be better understood, and its numerousobjects, features and advantages made apparent to those skilled in theart by referencing the accompanying drawings. The use of the samereference number throughout the several figures designates a like orsimilar element.

FIG. 1 depicts a blow-up view of a portable information handling systemhaving a tablet form factor in a housing with a heat-spreading outersurface;

FIG. 2 depicts a side cutaway view of a housing material having aheat-spreading outer surface;

FIG. 3 depicts a flow diagram of a process for assembly of a housing foran electronic device having a heat-spreading outer surface; and

FIG. 4 depicts a side cutaway view of a housing material having aheat-spreading outer surface.

DETAILED DESCRIPTION

An electronic device, such as an information handling system, has ahousing with a heat-spreading outer surface that minimizes the impact ofhot spots on an end user interacting with the housing. For purposes ofthis disclosure, an information handling system may include anyinstrumentality or aggregate of instrumentalities operable to compute,classify, process, transmit, receive, retrieve, originate, switch,store, display, manifest, detect, record, reproduce, handle, or utilizeany form of information, intelligence, or data for business, scientific,control, or other purposes. For example, an information handling systemmay be a personal computer, a network storage device, or any othersuitable device and may vary in size, shape, performance, functionality,and price. The information handling system may include random accessmemory (RAM), one or more processing resources such as a centralprocessing unit (CPU) or hardware or software control logic, ROM, and/orother types of nonvolatile memory. Additional components of theinformation handling system may include one or more disk drives, one ormore network ports for communicating with external devices as well asvarious input and output (I/O) devices, such as a keyboard, a mouse, anda video display. The information handling system may also include one ormore buses operable to transmit communications between the varioushardware components.

Referring now to FIG. 1, a blow-up view depicts a portable informationhandling system 10 having a tablet form factor in a housing 12 with aheat-spreading outer surface. Information handling system 10 processesinformation with processing components disposed in housing 12. Forexample, a motherboard 16 supports a CPU 18 and RAM 20 within housing 12and provides communication between CPU 18 and RAM 20 to store andexecute instructions. Persistent storage of information is provided by asolid state drive 22 and power to run the processing components isprovided by an integrated battery 24. A touchscreen display 26 enclosescomponents disposed in housing 12 and also provides an interface for endusers to view information as images and input information as touches. Inthe example embodiment depicted by FIG. 1, temperatures within housing12 are managed by passive thermal dissipation. In alternativeembodiments, alternative form factors for housing 12 and active thermaldissipation may be used, such as a clamshell laptop form factor thatincludes a cooling fan, a convertible tablet form factor or a desktopform factor.

Housing 12 includes a heat spreading outer surface 28 that readilyconducts thermal energy parallel to the surface in X and Y axes but haslimited conduction of thermal energy perpendicular to the surface in a Zaxis. For example, heat spreading outer surface 28 is graphene or othernano-structure carbon materials with limited Z axis thermalconductivity, such as carbon nanotubes. Heat-spreading outer surface 28reduces the risk of end user discomfort due to hot spots of concentratedthermal energy located at the outer surface of housing 12. For example,CPU 18 typically produces more excess thermal energy than othercomponents and the thermal energy can pass through housing 12 toconcentrate in the area of the housing outer surface that is proximateCPU 18. A graphene outer surface 28 spreads the thermal energy acrossthe surface of housing 12 so that heat does not concentrate in anyparticular location, such as proximate the position of CPU 18. Agraphene outer surface 28 also reduces the impact of thermal energy onan end user by having limited thermal conductivity out of the housing ina Z axis towards an end user's skin. For example, graphene thermalconductivity in the X and Y axes is approximately 300 W/mk versus lessthan 0.2 W/mk in the Z axis. In one embodiment, a graphene outer surface28 is used over only a portion of housing 12 as needed where hot spotstend to form, such as proximate CPU 18.

Referring now to FIG. 2, a side cutaway view depicts a housing materialhaving a heat-spreading outer surface 28. Housing 12 has a substrate 30of one or more materials that support a graphene outer surface 28exposed at the exterior of housing 12. In the example embodiment, theinner surface 32 of housing 12 is formed with a carbon fiber laminatematerial layer 34 having a thickness of substantially 0.8 mm thatprovides structural soundness. In alternative embodiments, carbon fiberthickness may vary from between 0.1 mm and 2 mm, and the aerogelthickness may vary from between 0.3 mm and 2 mm. A silica aerogel layer36 couples with carbon fiber laminate layer 34 towards the inner surface32 of housing 12 and to graphene outer surface 28 towards the exteriorof housing 12. Silica aerogel is a silicon based material with lightweight and poor thermal conductivity, which reduces conduction of heatfrom inner surface 32 to outer surface 28. Silica aerogel isstructurally a relatively weak material so that the carbon fiberlaminate material provides structural strength while the aerogelprovides thermal insulation. In one embodiment, graphene outer surface28 couples to silica aerogel layer 36 with an adhesive that addsapproximately 0.2 mm of thickness to the material. As an alternative,silica aerogel and graphene are coupled with a polyurethane and/or othertypes of stiff adhesive bonding agents using a laminate press at 200degrees Celsius to obtain bonding so that graphene outer layer 28effectively adds no thickness to housing 12. Infrared gun treatmentafter assembly of substrate 30 aids in bonding of the material layers.In one alternative embodiment, silica aerogel is sandwiched betweenlayers of carbon fiber or other materials that couple to graphene outersurface 28 instead of the aerogel. In other alternative embodiments,insulating materials other than aerogel may be used. As depicted in FIG.2 and other embodiments, the graphene outer surface may only provide aportion of a housing outer surface with other parts of the housing madefrom ceramic, composite, plastic, carbon fiber, aluminum, magnesium orother materials that abut against or overlap some or all of the grapheneouter surface. Generally, graphene and similar materials may flake offthe outer surface if coupled to the outer surface untreated, so thegraphene outer surface may include various polymer treatments to ensureits stability.

Referring now to FIG. 3, a flow diagram depicts a process for assemblyof a housing 12 for an electronic device having a heat-spreading outersurface 28. The example embodiment depicted by FIG. 3 uses carbonaerogel instead of a silicon aerogel in order to obtain a thinnersubstrate 30. Carbon aerogel is substantially 20% stronger and 80%smaller than silica aerogel and has similar thermal insulatingproperties. In the example embodiment depicted by FIG. 3, first andsecond carbon fiber layers 34 sandwich one or more carbon aerogel layers38 to form substrate 30. Carbon fiber layers 34 couple to the carbonaerogel layer 38 using a pre-preg process with application of heat andpressure to form a contiguous material, such as a polycarbonate basedpre-preg process and pressing at 200 degrees Celsius. In the exampleembodiment, first and second layers of carbon fiber sandwich a polymercarbon aerogel layer 38 to form material of substantially 0.6 mmthickness. A laminate of graphene 28 couples to a carbon fiber layer 34to form an outer housing surface, such as with an adhesive that adds 0.2mm of thickness. In alternative embodiments, graphene outer surfacelayer 28 may couple to a different material of substrate 30, such asanother layer of aerogel material. A total housing thickness ofsubstantially 0.8 mm is achieved in the example embodiment depicted byFIG. 3 where adhesive coupling of graphene outer surface layer 28 addssubstantially 0.2 mm. By comparison, use of a silica aerogel wouldresult in a housing thickness of substantially 1.2 mm.

Referring now to FIG. 4, a side cutaway view depicts a housing materialhaving a heat-spreading outer surface 28. In the example embodimentdepicted by FIG. 4, a single carbon fiber layer 34 supports a singlecarbon aerogel layer 38, which couples to a graphene outer surface 28.Carbon fiber layer 34 is a laminate having a thickness of substantially0.8 mm to provide structural support for housing 12. Carbon aerogel andgraphene layers 38 and 28 have a combined thickness of substantially 0.3mm to insulate thermal energy from passing to the housing exterior andto spread thermal energy that does pass to outer surface 28 so that hotspots do not form. Carbon aerogel layer 38 and graphene layer 28 coupletogether with polyurethane so that an adhesive is not needed with theadditional thickness associated with adhesive use. Substrate 30 islaminated using a press at 200 degrees Celsius and post press treatmentwith an IR gun for additional bonding. In alternative embodiments,alternative substrate materials may be used to provide structuralsupport and insulation, and alternative heat spreading materials may beused on the outer housing that spread heat in X and Y axes whilelimiting thermal transfer in a Z axis. The amount of insulation and theextent of heating spreading material may be altered to achieve desiredhousing characteristics.

Although the present invention has been described in detail, it shouldbe understood that various changes, substitutions and alterations can bemade hereto without departing from the spirit and scope of the inventionas defined by the appended claims.

What is claimed is:
 1. A method for manufacture of an electronic devicehousing, the method comprising: forming a substrate into at least aportion of the electronic device housing; and coupling graphene to atleast a portion of the outer surface of the substrate; wherein formingthe substrate further comprises coupling at least one layer of carbonfiber and one layer of aerogel.
 2. The method of claim 1 furthercomprising assembling a processor and memory into the electronic devicehousing, the processor and memory interfaced to process information. 3.The method of claim 1 wherein coupling graphene further comprisescoupling the graphene to the aerogel layer.
 4. The method of claim 1wherein coupling graphene further comprises coupling the graphene to thecarbon fiber layer.
 5. The method of claim 1 wherein coupling graphenefurther comprises coupling the graphene to the aerogel withpolyurethane.
 6. The method of claim 5 wherein the aerogel comprises asilica aerogel.
 7. The method of claim 5 wherein the aerogel comprises acarbon aerogel.
 8. A method for forming an electronic device housing,the method comprising: laminating carbon fiber to form a first layer ofthe electronic device housing; coupling an aerogel to the carbon fiberto form a second layer of the electronic device housing; and couplinggraphene to the aerogel to form an outer surface of the electronicdevice housing.
 9. The method of claim 8 wherein the aerogel comprises acarbon aerogel.
 10. The method of claim 9 wherein coupling graphenefurther comprises coupling the graphene and aerogel to the carbon fiberwith polyurethane.
 11. The method of claim 8 wherein the aerogelcomprises a silica aerogel.